1. Field of Invention
The present invention is generally related to amplifier circuits, and more particularly to cascode type amplifiers.
2. Description of the Related Art
Amplifiers are typically fabricated on integrated circuits for a wide variety of electronic applications including the amplification of analog signals. A class of such amplifiers, identified as cascode amplifiers is ideally suited to integrated circuits due to their high gain. Cascode amplifiers conventionally comprise two transistors the main conductions paths of which are either serially coupled so that both the input transistor and cascode transistor carry the same quiescent current in which case the amplifier is said to have a telescopic cascode design or parallel coupled so that the quiescent currents of input transistor and cascode can be independently controlled in which case the amplifier is said to have a folded cascode design. Either design may be implemented with a single ended or differential input.
In high frequency applications and in particular high frequency applications requiring multiple stages of amplification; the performance of these amplifiers is degraded by parasitic and other capacitances in each stage, the cumulative effect of which is to increase settling time and decrease the stability of the amplifier. What is needed is a method and apparatus for improving the high frequency performance of cascode amplifier designs.